In many signal conditioning systems especially communication links, received information bearing signals are subject to amplitude adjustment using a VGA.
Amplitude adjustment or so called gain adjustment of an incoming signal by a VGA is used to reach an amplitude level well above the noise and offset thresholds; or, otherwise, it may not be feasible to perform further post processing of the incoming signal, such as adaptive equalization. On the other hand, amplitude adjustment by the VGA may detrimentally affect the incoming signal quality by introducing bandwidth reduction, non-linearity or distortion. Distortion is difficult to compensate using linear circuit techniques.
As such, it is desirable to devise an amplitude adjustment scheme using a VGA that is digitally controlled (or adjusted) such that the VGA is suitable for high bandwidth and high linearity applications with wide amplitude adjustment range.